Two aluminum plates with 99.99 mass% purity with different hydrogen contents of 0.17 and 0.41 mass ppm were hot-rolled to 10 mm in thickness, cold-rolled by 99% to 130 μm in thickness, annealed at 250°C for 2 h, cold-rolled by 15% to 110 μm in thickness and finally annealed, which is similar to commercial processes of high purity aluminum foils for electrolytic capacitors. The foils were subjected to optical macro- and micro-scopies, thermal desorption spectroscopy (TDS), hydrogen micro-print technique (HMPT) and electron back-scattering diffraction pattern (EBSP) analysis and the effect of impurity hydrogen on the growth of off-cube grains in a recrystallized microstructure with a strong cube texture was investigated. It was confirmed that abnormal grain growth of off-cube grains becomes more conspicuous with the increase in the amount of impurity hydrogen in the original ingot. The HMPT analysis showed that hydrogen concentration in the cube-oriented region was larger than in the off-cube grain. The grain size in the cube-oriented region decreased with decreasing hydrogen content. From these facts and the result of TDS, supersaturated hydrogen atoms were presumed to segregate to low angle grain boundaries, the boundaries between cube-oriented grains, which can provide the driving force for the abnormal grain growth.

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The thermo-mechanical fatigue life and microstructural change under a compression-tension thermo-mechanical cyclic loading of a surface-hardened Al-Si-Mg alloy casting are investigated. A surface cold working technique using steel balls is utilized for the surface hardening. Out-of-phase type thermo-mechanical fatigue tests have been performed with the temperature range of 323–523 K and the applied mechanical strain range of 0.75–2.0%. The surface-hardened material exhibits better thermo-mechanical fatigue property especially in a low cycle regime, together with higher generated stress, suggesting that it is even superior under stress-controlled loading. The differences in the stress–strain hysteresis loops and hardness variation near specimen surface between the materials with and without surface hardening have not vanished until final fracture. The observed difference in the thermo-mechanical property is attributed to some microstructural differences. The effects of damaging at the silicon particles to this difference are also investigated using the high-resolution microtomography technique. It has been clarified by microstructural observations that recovery and recrystallization are suppressed in the surface-hardened material. It can be inferred that such thermal stability is attributed to the multi-axial deformation by a combination of the surface hardening and the thermo-mechanical loading.

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Using conventional deep drawing method, it is difficult to make square cups taller than the length of straight side of punch in only one stage drawing. This is because, in case of using a conventional, the drawing resistance of blank material is too high to draw material into die hole by punch. From simple consideration, by using the developed blank, the flange portion of which is divided into four elements, the drawing resistance of blank material can be reduced considerably, and so this problem can be overcome. In this investigation, a deep drawing process of square cup was attempted using a developed blank instead of an octagonal or ellipse blank. By introducing assumption of the constant arc length, the shape of developed blank was designed. It was clarified that, when developed blanks with appropriate shape was employed, very tall square cups could be obtained in one stage drawing.

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Tubes that have the rib internally are used as car parts, for example, structural component, radiator, shock absorbers, and so on. The existence of some holes at the rib enhances the function and value of the tubes. But, the tube with holed rib can not be formed by conventional extrusion. Then, we propose a method that extrudes with a ready made rib. The rib is a machined sheet metal with holes. While the tube is extruded, the rib is fed through a slit of mandrel. Tube and sheet are joined at the same time during extrusion. The mandrel has slit and guide. A guide position h that is a distance from die surface to front edge of the guide is a dominant parameter in this research. When guide position h is controlled, metal flow can be adjusted. We carried out an experiment to clarify the effect of guide position on joining by using A1050. Then, a tensile test clarified that joining strength between tube and rib is 40% of base material. Moreover, flatness was observed in measuring the outside diameter and the inside diameter of the tube.

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